Balanced slide-valve.



PATENTED 001-17, 1905' I; B. ALLPRBE. BALANCED SLIDE VALVE.

APPLIOATION FILED SEPT. 9, 1901.

Eff W u d 1! M a J z a fi INVENTOR. B A1 Jg A TTORNEY.

WITNESSES .1

JAMES B. ALLFREE, OF INDIANAPOLIS, INDIANA.

BALANCED SLIDE-VALVE.

Specification of Letters Patent.

Patented Oct. 17, 1905.

Application filed September 9, 1901. Serial No. 74,794.

To aZZ whom it may concern:

Be it known that I, J AMES B. ALLFREE, a citizen of the United States, residing at In.- dianapolis, in the county of Marion and State of Indiana, have invented certain new Improvements in Balanced Slide-Valves for Engines Operated by Steam or Other Fluid Pressures, of which the following is a specification.

My invention relates to improvements in balanced slide-valves in which a hood or pressure-plate is provided and adapted to fit in a steam-tight contact to the back of my valves, the valve being of segmental shape circumscribed by the arc and chord of a circle representing less than one-half of a circle in cross-section, the plane side of the valve preferably engaging with the valve-seat and convex back with the concave surface of pressure-plate, a further object being to provide such construction that with one set of patterns and plan of construction the steam or other actuating fluid may be admitted either from the inside or outside of valve, making it possible to control the second cylinder of a twin engine or the low-pressure cylinder of a cross compound engine with one governor, the cranks being set diametrically opposite each other, andfor the further object of providing an increased wearing-surface 0n the back or outside of valve, as experience shows that the greatest wear in such balanced slidevalves is on the side next to the pressureplate; and a further object is to provide a means whereby wear between the pressureplate and valve may be readily taken up by planing or scraping the face or plane side of the pressure-plate, thus taking up in all directions whatever looseness the wear may have caused. To this end the valve is made less than one-half of a circle and of such proportions as experience has shown to be nearest correct. It will readily be observed that as a result of this form by planing or scraping off the plane surface of the pressure-plate the valve will be readily brought tight, as a given amount taken from face of hood will diminish the chord or width of concavity of said hood an equal amount, as when leakage occurs it is found that the curvature of the valve fits perfectly the curvature of the hood, it being necessary, therefore, only to reduce the depth of the concavity of the hood by planing or scraping the plane surfaces of said hood that joins with valve-seat.

A further object is to construct a balanced valve so as to require the least amount of machine-work, this form being such as to permit of two valves being turned in an ordinary lathe at a time and two pressure-plates bored to precisely the same dimensions at one time in an ordinary lathe, which may be so perfectly done that practically no handwork will be required; and as a further object it is desired to get the greatest amount of admission and exhaust area with the lowest clearance and lightest weight for the moving parts,

as it is well known that perfect regulation in an automatic engine becomes impossible with a valve that is too heavy, and it is therefore desirable and important that the valve be so designed and constructed as to reduce its weight to the minimum.

I attain these objects by the constructio illustrated in the accompanying drawings, in the several figures of which similar letters of reference denote similar parts.

Figure 1 is a side elevation of back and section of hood or pressure-plate and cylinder; Fig. 2, sectional view of same on line 2. Figs. 3 and i show enlarged detached end and side views of my valve. Figs. 5 and 6 are further enlarged end and side views of same, partly in section. Fig. 7 is a detached top view of a packing-strip and its joint-block. Fig. 8 is an enlarged side view of the packing-strip and block and a top view of said block detached.

represents the cylinder; at, the steamports; (f, the valve-seat; a live-steam chamber, in this casein which I represent a valve, in which the steam-pressure is admitted to the inside of the steam-valve; a the piston; a the cylinder-head.

6 is the valve, of segmental form with plane surfaces adapted to register with ports in valve-seat c and the upper or convex surfaces being for the advantage of construction preferably the arc of a true circle.

0 is a pressure-plate concave at 0, the concave surface engaging with the convex side of said valve.

The plane lower surfaces of hood or pressure-plate c are fitted and secured by a series of screws 0 taking into the valve-seat at (0 0 represents ribs to strengthen said pressureplate.

The valve 6 is in this case,as shown, formed of two head-pieces tied together with stem or bar I) at such length as to permit of having very short and direct steam-ports, and thereby securing very low clearance due to the ports,

and in valves of the larger sizes each head of said valve is provided with two sets of packing-strips 6 near each edge, and the span between said strips is recessed so as to form a continuous channel or recess I), skirting the convex back of the valve from point to point, but not being so deep at the points as to uncover the ports at any time, said channels being provided with openings Z2 communicating with bottom or face side of the valve at such point that when the valve moves to admit steam to the cylinder-port said 'opening is in position to allow steam to enter into said channel, which we will call the balancingchamber, and whereas I have also recessed or chamfered the ends of the valve, as seen at 5 so as to bring the edge of the face of the valve directly even with the edge of the packingstrip, so that the valve is balanced under all conditions. The said packing -strips e are fitted in grooves in which are fitted packing-blocksfithrough which the grooves f are milled, and the said strips are abutted Within said block and are provided with a coil-spring 6 set in suitable holes drilled in the abutting ends, the outer ends of said strips being beveled at bottom side and fitted to suitablyinclined surfaces at a, all combined to act so that when said stripwears at any point the pressure of spring keeps it up against hood or pressure-plate d, and the block f being also provided with aspring g, a flat spring in this case, whereby all wear is compensated for, as the block and strips carried are thus constantly held against said pressure-plate.

At f are shown top and sectional side views of a packing-block provided with sloping bottom surfaces whereupon the middle or inner ends of suitably-beveled packing-strips rest, as seen in Fig. 8.

There is no certain proportion as to what part of a circle may be represented by the cross-section of my valve; but from results of experience I prefer to employ that portion represented by about one hundred to one hundred and ten degrees of a circle. This assures a good strength of metal at the sharp edges of the valve and at the same time facilitates the process of taking up wear, as stated.

Having described my invention, what I claim as new, and desire to secure by Letters Patent, is

In a balanced slide-valve, the combination with a segmental valve, a concave hood or pressure-plate, a plane valve-seat with which said valve registers and to which said hood or pressure-plate is secured, balancing channel or recess in convex surface of said valve, packing-strips at each side of said channel, a packing-block adapted to form steam-tight joint at junction of said strips, a spring adapted to press said block with said strips against the pressure-plate and beveled bearing-joints at outer edges of valve for end of said strips and suitably-beveled surfaces at ends of said strips, whereupon they are adjustable for wear; all combined to operate as set forth.

In testimony that I claim the foregoing I subscribe my name hereto, in the presence of witnesses, this 24cth day of August, A. D. 1901.

JAMES B. ALLFREE.

Witnesses:

E. B. HETZEL, A. L. TEETOR. 

